Go Back   Steve's Digicams Forums > Misc Forums > New Technology

Reply
 
Thread Tools Search this Thread
Old Jan 31, 2003, 9:50 PM   #1
Senior Member
 
BillDrew's Avatar
 
Join Date: Jun 2002
Location: Hay River Township, WI
Posts: 2,512
Default Camera tests

Did some test shooting and am going to try to explain this graph:

I shot the same gray card with constant light, cropped out a 200x200 chunk of the middle of each one, and used Max Lyons’ Thumber’s (http://www.tawbaware.com/index.html - shareware) Noise Analysis Report to measure the average RGB value with all the f/stops and shutter speed available to me (I dropped many that stuck at zero or 256 from the graph). The X-axis zero value is the exposure the in-camera light meter read as the proper exposure.

I suspect that much of the “scatter” is due to the camera not reporting the real value of the f/stop. In any case it is less than plus/minus half a stop.

I think that graph shows why tending toward underexposure is a good idea with a digicam – or at least with mine. At plus three stops, the image has gone to a pure white – blown out. Though it is tailing toward zero, at minus four stops, there is still some variability left. Blowout (256 – pure white) happens abruptly while blocking (zero – pure black) happens gradually.

The graph clearly shows why it is possible to dig an image, albeit noisy, out of an underexposed image while an overexposed one is simply gone.

The newly announced Fuji CCD (http://www.steves-digicams.com/pr/fuji_01222003_pr.html here at Steve’s and http://www.dpreview.com/news/0301/03...superccdsr.asp at dpReview) looks like it is designed to deal with the issue of the sharp “knee” to blowout. Should be interesting to see in a real camera.
BillDrew is offline   Reply With Quote
Sponsored Links
 
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off



All times are GMT -5. The time now is 11:10 AM.